1. Field of the Invention
The present invention relates to a liquid discharge head which performs a recording operation by discharging a liquid to a recording medium such as recording paper as well as to a manufacturing method for the liquid discharge head.
2. Description of the Related Art
Apparatus equipped with a liquid discharge head such as an inkjet recording head involve relatively low running costs and readily lend themselves to downsizing. Furthermore, such apparatus readily support color image recording using inks of multiple colors as liquids, and are thus widely used as computer-related output devices and introduced commercially.
Among recent liquid discharge heads, a head of a wide type is known which performs recording on a line by line basis using a large number of discharge ports adapted to discharge liquids and arranged in a width direction of a recording medium over a width equal to a recording width. Such a wide liquid discharge head is disclosed in Japanese Patent Application Laid-Open No. 2007-296638, and an exploded perspective view thereof is illustrated in FIG. 1 of the present application. The liquid discharge head includes a supporting substrate H1200, a number of recording element boards H1100 on which a large number of discharge ports (not shown) adapted to discharge liquids are formed, and an electrical wiring board H1300 adapted to supply electrical signals to the recording element boards H1100, where the recording element boards H1100 and electrical wiring board H1300 are arranged on the supporting substrate H1200. Specifically, the recording element boards H1100 are arranged in a staggered manner and have overlapping regions L along a recording direction (moving direction of a carriage which supports the head). The liquid discharge head is configured such that there will be no clearance in the recording direction between an end of a discharge port group on each recording element board H1100 and ends of discharge port groups on adjacent recording element boards H1100.
Detailed configuration of the liquid discharge head will be described below with reference to FIGS. 1, 2A, 2B, 2C and 3.
FIGS. 2A to 2C are schematic diagrams showing an electrical wiring board H1300 and recording element board H1100 of a conventional liquid discharge head and their surroundings. FIG. 2A illustrates a state before wires H2000 adapted to electrically interconnect the electrical wiring board H1300 and recording element board H1100 are sealed with a sealing member. FIG. 2B is a schematic plan view showing a state after the transmitting wires H2000 are sealed. FIG. 2C is a schematic sectional view taken along line 2C-2C in FIGS. 2A and 2B. The electrical wiring board H1300 supplies the recording element board H1100 with electrical signals such as a recording signal from a main body of a recording apparatus (not shown). The electrical wiring board H1300 has predetermined wires and an opening H1303. A terminal group H1302 corresponding to a terminal group H1103 of the recording element board H1100 is formed on both sides of the opening H1303. Incidentally, in FIG. 2A, in which no sealing member is applied, the supporting substrate H1200 which supports the recording element board H1100 and electrical wiring board H1300 is visible through the opening H1303. A flow path H1101 adapted to guide a liquid to the discharge ports is formed in the recording element board H1100. The recording element board H1100 is placed by aligning the flow path H1101 with a liquid supply port H1201 formed in the supporting substrate H1200 and is firmly bonded to the supporting substrate H1200 by a first adhesive. Then, the electrical wiring board H1300 is firmly bonded to the supporting substrate H1200 by a second adhesive so as to position the recording element board H1100 in the opening H1303 of the electrical wiring board H1300. The recording element board H1100 and electrical wiring board H1300 are electrically interconnected using the wires H2000 made of gold.
There is a clearance between the recording element board H1100 placed in the opening H1303 of the electrical wiring board and side walls of the opening H1303 of the electrical wiring board. The clearance, i.e., space around an outer periphery of the recording element board H1100 is filled with a first sealing member H1304. This enables sealing and protecting the periphery of the opening H1303 of the electrical wiring board H1300 and side faces of the recording element board H1100 and thereby prevents corrosion resulting from contact with minute liquid droplets scattered when a liquid such as ink is discharged.
Besides, at opposite ends in longitudinal direction (X direction in FIG. 2A) of the long-sized electrical wiring board H1300, a second sealing member H1305 is applied at the position of the wires H2000 electrically interconnecting the electrical wiring board H1300 and recording element board H1100. Consequently, electrical connections including the peripheries of the terminal groups H1103 and H1302 of the recording element board H1100 and electrical wiring board H1300 and the wires H2000 are protected from corrosion resulting from contact with a liquid such as ink droplets.
In the liquid discharge head illustrated in FIGS. 2A to 2C, when the sealing members H1304 and H1305 are applied, application amounts are adjusted through adjustment of pressure applied to the sealing members H1304 and H1305. However, viscosity of the sealing members H1304 and H1305 vary with the temperature and time, which may cause variations in the application amounts of the sealing members H1304 and H1305.
When there are variations in the application amounts, it becomes difficult to apply desired amounts of the sealing members H1304 and H1305. Consequently, as illustrated in FIG. 3, the second sealing member H1305 intended to seal the wires H2000 could fall short of a required application amount, exposing part of the wires (hereinafter also referred to as an exposed portion) H2001 from the sealing member H1305.
If part of the wires H2001 is exposed, the exposed portion H2001 comes into contact with water, air or ink, and could get chemically corroded by the water, air or ink. In particular, adhesion of liquid ink can pose a problem in that chemical corrosion will have a significant impact, degrading electrical characteristics of the wires.
Normally, the liquid discharge head is equipped with a cleaning mechanism adapted to wipe a face (hereinafter referred to as a discharge port side surface) on which the discharge ports are formed. When the cleaning mechanism comes into operation, the exposed portion H2001 of the wires not protected by the sealing member H1305 comes into direct contact with a wiping rubber blade, experiencing a mechanical load. In that case, the wires H2000 could get broken or deformed.
Thus, generally, the application amount of the sealing member H1305 is increased to prevent exposure of the wires H2000. However, increasing the application amount of the sealing member H1305 increases height D01 of the sealing member H1305 on the recording element board H1100 as well. For the liquid discharge head, the height D01 of the sealing member H1305 is a determining factor of an interval between the recording medium and discharge port side surface. That is, when the height D01 of the sealing member H1305 is increased, distance between the recording medium and discharge port side surface is increased accordingly. This reduces landing accuracy of the liquid, making it difficult to do high-quality printing.
Generally, with the liquid discharge head, to remove liquid droplets and dust adhering to the discharge port side surface, the discharge port side surface is cleaned using a rubber blade or the like. In so doing, if the height D01 of the sealing member H1305 is large, there can be a problem of decreased cleaning effects at and around the discharge port side surface.
From this point of view, it is desired to seal the wires H2000 which contribute to electrical connection with a sealing member so as not to expose the wires. The height of the sealing member can be kept as low as possible.
Japanese Patent Application Laid-Open No. H08-336963 clearly points out a problem in that a sealing member is drawn to a center of a sealing portion, exposing ends of wires. To solve this problem, Japanese Patent Application Laid-Open No. H08-336963 proposes to form dummy wires on the outside of principal wires in order to prevent an interface of a sealing member in a direction of a two-dimensional spread on a coated surface from deviating from a desired position, where the dummy wires are wires which do not contribute to electrical connection while the principal wires are wires which contribute to electrical connection.
Also, Japanese Patent Application Laid-Open No. H07-335680 proposes, in wire bonding, to form dummy wires whose apex (highest point) is higher than principal wires to protect the principal wires from external forces.
However, although the configuration described in Japanese Patent Application Laid-Open No. H08-336963 is effective against the problem of two-dimensional spreading or narrowing of the sealing member along the coated surface, the configuration is not effective in reducing variations in the height of the sealing member. Thus, this configuration cannot solve the problem of exposed principal wires when the application amount of the sealing member is small.
Also, with the configuration described in Japanese Patent Application Laid-Open No. H07-335680, principal wires are formed to be higher than dummy wires in part of wire bonding regions. Consequently, the problem of exposed principal wires cannot be solved when the application amount of the sealing member is small as described above.
In order to keep the height of the sealing member as low as possible, it is necessary to minimize the amount of sealing member applied to coat the principal wires, but if the application amount decreases due to its variations, the problem of exposed principal wires can arise.